I did it for my house 8 months back. Your case is an apartment? For smaller area, usually the installers charge one lump sum. This is due to the transport and set up cost. You may want to ask for alternative quotations.

I spent RM4 for every square foot of gypsum board. The price was slightly higher due to my tall 3.6m ceiling. I thought the common psf is around RM3.60 - 4.00 at Klang Valley. The workers needed scaffolding, which was an extra charge. For the metal access panel (below those floor trap), it cost RM120 each. Making an open hole was RM5 per hole. The L box, sized 100mmx150mm, was priced at RM15 per foot.